There are various methods for the chip removing cutting of gearwheels. The correspondingly designed machines are referred to here as gear cutting machines.
It is known that the temperature of the gear cutting machine increases with time because of various procedures in the machine. In continuous operation of a machine, it reaches a so-called steady-state temperature. The steady-state temperature results in a thermally stationary state. In this state, the temperature of the machine has thermally stabilized. A stabilization of the heat flows thus occurs over time, which results in a stationary state.
It is also known that inaccuracies can occur in a machining process because of thermal expansion processes. This is because, inter alia, the greatly varying elements of the machine experience a thermal expansion with increasing temperature. A corresponding thermal contraction occurs upon cooling. On the one hand, the dimensions of the individual machine elements change with increasing temperature of the machine. Since numerous elements are connected to one another in a machine, tensions (and warping) can occur because of different coefficients of expansion, which are displayed in nonlinear expansion behavior, which cannot be computed accurately, of the machine.
The thermal behavior of a machine is influenced by the effect of heat sources and heatsinks. A differentiation is made in the case of thermal effects between internal and external influences. For example, the heat emission of motors is considered to be an internal influence. A further internal influence results from the cutting interaction of a tool with a workpiece, because mechanical energy is converted into heat here. External influences are, for example, the ambient temperature in a machine shop.
It is immediately apparent that the length, for example, of a cantilever, which is connected on one side to a machine stand, for example, increases with increasing temperature. Such a cantilever experiences a linear expansion in the longitudinal direction. In the case of complicated machine elements and more complex geometries, for example, a spindle bearing, the relationships are significantly more complex.
The operating accuracy of chip producing machines is substantially dependent on how accurately the movements in the three-dimensional space between the tool and the workpiece can be executed. Finally, relative deviations during the movement of the tool relative to the workpiece result due to all temperature-related effects. These relative deviations result in deviations on the workpiece.
Productivity and accuracy are important aspects of machine tools. The thermal accuracy of machines is gaining more and more significance in consideration of strongly increased demands in the matter of manufacturing precision. Particularly in the case of small manufacturing batches and therefore changing machine tasks, a thermally stable state cannot be achieved. In the case of machines which are in continuous use, the accuracy gains significance above all after an interruption. Moreover, one wishes to reduce the discards which typically occur after an interruption until the machine has again reached the steady-state temperature to some extent. Thus, in addition to accuracy, this also relates to questions of cost-effectiveness.
One common approach is to keep machine and surroundings at a consistent temperature level. The deformation of the machine may be avoided by way of a uniform temperature. For this purpose, on the one hand the machine shop has to be climate-controlled and, on the other hand, the machine has to be continuously operated. The expenditure in costs and energy is correspondingly high.
Another approach is monitoring the deformation of the machine by way of integrated sensors. On the basis of a mathematical model, in which the data of the sensors are further processed, the foundation can be formed for an approximate prediction of the flaws, which would arise on the workpiece. If these flaws are known, the machine can thus adapt accordingly and compensate for the flaws. The expenditure is also high here. Moreover, there have been no technological approaches up to this point which meet the high accuracy requirements.
In consideration of the above statements, the following object results. It relates to finding an approach which enables compensating for temperature-related changes of a machine. Above all, this relates to improving the accuracy of a machining process in a machine immediately after an interruption, to thus reduce the discards. A pause which is preferably longer than 15 minutes is referred to as an interruption.